The present invention relates to a wire binder wherein a binding wire is supplied around a plurality of articles such as reinforcement steel rods or the like to be bound so as to allow the binding wire to be circularly wound around the articles, a part of the circularly wound binding wire is seized and twisted so as to allow the circularly wound wire to be tightened, and thereafter, the binding wire is released from the seized state.
A wire binder as disclosed in a Japanese Examined Patent Publication No. 59-39027 has been hitherto known as a typical conventional wire binder of the aforementioned type. This wire binder is constructed such that a binding wire wound around a bobbin is unreeled from the latter so as to allow it to be wound around a plurality of articles such as reinforcement steel rods or the like to be bound especially at their intersections, and thereafter, a part of the circularly wound wire is seized and twisted to tightly bind the articles together. Wire supplying, wire cutting and wire twisting and other operations are sequentially performed by actuating a single start lever.
With the conventional wire binder constructed in the above-described manner, as a trigger switch is actuated with an operator's hand, a driving motor is activated, causing a cam to be rotationally driven. While the cam is rotated by one revolution, various mechanism in the wire binder are sequentially actuated. In other words, a predetermined length of binding wire is supplied around a plurality of articles to be bound via an arc-shaped guide, and thereafter, a twisting shaft is rotated by a predetermined number of revolutions to tightly bind the articles with the binding wire.
However, since the twisting shaft is always rotated by a given number of revolutions, in case that the binding wire has a small diameter, there arises a malfunction that the articles fail to be bound together with the binding wire due to the weakly tightened state. To cope with employment of a binding wire having a larger diameter, the wire binder is modified such that it additionally includes a mechanism which serves to induce slippage between a twisting shaft and a driving shaft after a predetermined magnitude of twisting torque is reached with the aid of a clutch or the like in a twist/rotate driving system. However, with this modified wire binder, a time which elapses during the occurrence of slippage is useless for each binding operation. In addition, there arises a problem that clutching sound is intermittently generated during the slippage, resulting in a working environment of the wire binder being deteriorated.
Particularly, since the foregoing type of wire binder is usually operated using a battery, when the twisting shaft is rotated with slippage, there arises another malfunction that the number of binding operations per one battery charge is reduced.
The Japanese Examined Patent Publication No. 59-39027 also shows a conventional wire binder having a typical conventional torque detecting mechanism including a clutch mechanism wherein raised portions are brought in engagement with the corresponding recessed portions by the resilient force of a spring spanned between an output shaft and a twist shaft in a speed reduction mechanism operatively connected to a motor shaft. Specifically, the conventional torque detecting mechanism is constructed such that when the loaded torque arising during the twisting operation reaches a predetermined value, the raised portions and the recessed portions are parted away from each other against the resilient force of the spring, causing slippage to occur between the output shaft and the twisting drive shaft, resulting in any torque in excess of a predetermined magnitude of torque failing to be exerted on the twisting drive shaft.
With the conventional torque detecting mechanism constructed in the above-described manner, however, due to the fact that the clutch mechanism is disposed between the output shaft having a reduced speed and the twisting drive shaft, a large magnitude of torque is usually exerted on the clutch mechanism. Thus, there arises a necessity that the spring for bringing the raised portions in engagement with the recessed portions has a high intensity of resilient force. This leads to a problem that an assembling operation and an adjusting operation are unavoidably performed in a complicated manner.
In addition, it is necessary that a movable clutch member is arranged in the axial direction between the output shaft and the twisting drive shaft, and moreover, a spring for squeezing the clutch member and a mechanism for adjusting an intensity of resilient force of the spring are additionally arranged in operative association with the movable clutch member. Thus, there arises another problem that the foregoing mechanism is enlarged not only in size bust also in weight.
With respect to a tool adapted to operate with the aid of a rechargeable battery, since a motor having a large quantity of electricity consumption is rotated further after a predetermined magnitude of torque is reached with the tool, there arises a problem that the number of binding operations to be achieved per one electric charge is reduced, resulting in an operational efficiency being degraded.
The Japanese Patent Examined Publication No. 59-39027 further shows a wire binder for binding a plurality of articles to be bound using a binding wire wherein an arc-shaped guide portion is arranged on the front side relative to a wire supplying mechanism for successively supplying a long binding wire in the forward direction, the binding wire discharged from the foremost end of an arc-shaped guide portion is wound around a plurality of articles to be bound by several turns, and the articles are bound together by seizing and twisting a part of the X wound binding wire has been hitherto known as a typical binder of the foregoing type. With the conventional binder constructed in the above-described manner, since it is necessary that the binding wire is cut prior to the twisting after it is wound around the articles to be bound, a cutting mechanism is disposed at the fore end part of the arc-shaped guide portion. To actuate the cutting mechanism, a wire rope is extensively arranged along the arc-shaped contour of the guide portion wherein one end of the wire rope is connected to the cutting mechanism, while the other end Of the same is connected to an actuating mechanism in the binder.
However, with the system for cutting a binding wire by pulling a wire rope in the above-described manner, since the wire rope is elongated during each pulling operation, there arise malfunctions that the binding wire can not reliably be cut by the cutting mechanism, and moreover, reliability on the actuation of the cutting mechanism is degraded. In addition, there arises a necessity for arranging an adjusting mechanism to cope with the elongation of the wire rope. In practice, however, the adjusting mechanism should be readjusted frequently.
Since the wire rope is arranged along the arc-shaped contour of the guide portion, the cutting mechanism receives a large magnitude of resistance during each cutting operation. This leads to a problem that the wire rope is cut due to friction appearing between the wire rope and the guide portion, causing the cutting mechanism to be incorrectly actuated.
If the cutting mechanism is arranged in the linear region before the arc-shaped part of the guide portion, the cutting mechanism can be actuated using a rod without any appearance of the aforementioned problem. However, since a part of the cut binding wire remains still in the arc-shaped part of the guide portion, interference occurs between the guide portion and the bound part of the binding wire after the latter is twisted, resulting in workability of the binder being degraded.
A Japanese Patent Examined Publication No. Hei. 3-60989 teaches a conventional wire binder having an apparatus for controlling a twisting hook employable for a binder for binding a binding wire. According to the conventional wire binder, the apparatus is constructed such that a chucking member adapted to slidably move in the axial direction is arranged around the outer peripheral surface of a twist shaft having a hook for seizing a binding wire pivotally supported thereon so that the hook is opened or closed by slidable movement of the chucking member relative to the twist shaft. In addition, a cam mechanism is employed for the apparatus for slidably displacing the chucking member. This leads to a necessity for arranging a power transmission shifting mechanism which serves to rotationally drive the twist shaft as desired.
The conventional wire binder is required to locate the hook to assume a predetermined angle after completion of a series of binding steps. According to the conventional wire binder, a mechanism for opening the hook by rotating the twisting shaft in the reverse direction after completion of each binding operation, and at the same time, stopping the hook at a predetermined position by bringing the hook in engagement with an abutment member to stop the reverse rotation of the twist shaft by rotating the abutment member is used for the binder. However, with the mechanism as mentioned above, since the abutment member is arranged in the vicinity of a plurality of articles to be bound, there is a possibility that the abutment member is damaged or injured when it comes in engagement with the articles during each binding operation.